Method and apparatus for the delivery of gear pumps



J. LIPINSKI Nov. 2'7, 1956 METHOD AND APPARATUS FOR THE DELIVERY OF GEAR PUMPS Filed Aug. 5, 1954 ATTYJ.

NETHOD AND APPARATUS FOR THE DELIVERY 9F GEAR PUIVHS Johann Lipinsld, Pressbaum, near Vienna, Austria, assignor to Alex. Friedmann, Kommanditgesellschaft, Vienna, Austria Application August 5, 1954, erial No. 448,016 Claims priority, application Austria August 11, 1953 13 Claims. ((31. 103-41) In the known gear pumps, in which a medium is handled by interengaging spur or screw gears, the delivery asociated with a predetermined speed depends only on the predcterminded invariable dimensions of the gears and for this reason cannot be adjusted.

For some purposes, e. g. where such gear pumps are used as lubricating pumps, or as metering pumps, e. g. for oil burners or the like, a variable delivery is desirable either to obtain different delivery volumes or to compensate losses due to increased leakage at lower speed.

It is known to use only part of the capacity of gear pumps in order to obtain an intermittent discharge similarly as with piston pumps. To this end the discharge end of the gear pump is relieved periodically, e. g. by being connected to the suction end. In known constructions this is effected, e. g. by forming part of the teeth of the cooperating gears with apertures which cause an interruption of the discharge. It has also been suggested to subdivide the pump gears into gears having different numbers of teeth and mounted in axial alignment on the same axis in order .to obtain a speed difference between the gears arranged one behind the ther on the shaft. in that case control ports formed in those gears and periodically registering to connect the discharge space with the suction space cause a periodical interruption of the discharge. In said known arrangements, however, only an intermittent discharge or discontinuous discharge characteristics was achieved by the periodical interruption of the discharge whereas they did not enable variation of the delivery rate of a gear pump from time to time and its adaptation to the demand.

It is an object of the invention to enable such adaptation of the delivery rate of a gear pump to the demand.

The A retired according to the invention for controlling the delivery of gear pumps operating with an alternating connection of the outlet to a space separate from the delivery passage, e. to a return passage, essentially consists in the variation of the delivery of the gear pump by a va ation of the ratio between the length of the discharge period and the length of the return or the like period. Thus larger or smaller part of the total capacity of the pump is branched oif for control purposes by ing the pump to feed through a longer or shorter period into a space separate from the outlet. In the simplest case that space separate from the delivery passage may a return passage leading to the reservior or to the suction end or the pump, but the fluid handled educe the delivery may also be put and branched Lil to r to any other use. Since such gear pump handles the fluid continuously and in the case of constant speed has a certain capacity, the subdivision of the handling period enables a precise subdivision of the capacity. The ratio between the period in which the pump feeds into the delivery passage and the period in which the handling is short-circul ted by the return of the fluid handled definitely determines the ratio between the quantity fed 2,771,844 Patented Nov. 27, 1956 to the delivery passage and the quantity returned, and thus determines the volumetric delivery of the pump.

Since only the ratio of the periods is decisive in which the pump feeds into the delivery passage and into the return passage, respectively, whereas the absolute length of said periods does not affect the setting of the delivery, those periods be selected with any desired length. The shorter these periods are determined and the more quickly they alternate, the more closely will the delivery of the pump approach continuous delivery. For this reason it appears desirable to make the absolute length of said period relatively small. Thus the maximum duration of a handling cycle should not substantially exceed the time of one turn of one of the pump gears. Preferably the total of the length of a delivery period and of the length of the subsequent return or the like period equals the tim of one turn of a pump gear so that during one turn of a pump gear the fluid handled is fed once into the delivery passage and once into the return passage. To vary the useful delivery rate of the pump one of these two handling periods may become Zero, if desired. For instance, if the return period is made zero, the full capacity of the pump can be passed into the delivery passage as a useful delivery rate; on the other hand, if the period in which the pump feeds into the delivery passage is made zero the useful delivery may interrupted completely and the entire capacity of the pump passed into the return passage.

Thus the invention enables the variation of the useful delivery of the gear pump in any desired way between the limits consisting of the full capacity of the pump and zero delivery. That variation may be effected by an arbitrary adjustment or automatically. In the latter case the ratio between the length of the delivery periods and the length of the return or the like periods may be varied according to the invention in dependence on the delivery counter pressure. Whereas previously an automatic regulation of the delivery of such pump in dependence on the delivery counter pressure was possible by an arrangement of pressure maintaining valves to reduce the delivery upon an increase of the delivery counter pressure, the invention enables also an increase of the length of the discharge period relative to the return or the like period and thus an increase of the delivery upon an increase of the delivery counter pressure, This is important, e. g., for lubricating pumps, where it is now possible when a lubricating line is clogged to increase the delivery and with it the pressure in the lubricating line in order to open the line.

A gear pump controlled by the method according to the invention is essentially characterized by a control member which is in drive connection with the pump and which during its motion alternately connects the discharge space of the pump to the delivery passage and to a return passage or the like and whose effective range can be adjusted arbitrarily or automatically. In the simplest case that control member is a rotary and axially movable valve member, which in a preferred embodiment of the invention is formed by the shaft of one of the pump gears itself.

According to the invention the valve arrangement comprises a control recess and the delivery passage and the return passage or the like open at axially spaced points into the cylindrical bore of the rotary valve member, which is axially displaceably mounted in its cylindrical guide bore to vary the delivery of the pump. The control recess of the rotary valve member is suitably in the form of an oblique groove closed in itself and extending all around the periphery of the rotary valve member, which groove connects the discharge space of the pump alternately to the delivery passage and the return passage as the rotary valve member revolves. The ratio between the length of the discharge period and the length of the return period is varied by an axial displacement of the rotary valve member.

In the drawing the invention is explained diagrammatically with reference to illustrative embodiments.

Figs. 1 and 2 show a gear pump formed with spur gears and provided with an arbitrarily adjustable control, Fig. 1 being a sectional view taken through the axes of the gears on line Ii of Fig. 2, and Fig. 2 being a section-al view taken on line Iili of Fig. i.

Fig. 3 shows a gear pump with an automatic control, in a sectional view taken through the axes of the gears.

Fig. 4 shows a similar embodiment as Fig. 3 but with an automatic control acting in the opposite sense.

in the embodiment shown in Figs. 1 and 2 the pump gears 1 and 2 are mounted in a working chamber in .ne casing which consists of three parts 3, 4 and 5 and which is held together by screws 6. The pump is driven through a drive shaft 7, which has inserted therein a transverse pin 9 engaging a groove 3 of gear 1. The shaft it) of the second pump gear 2 is also formed with a transverse pin 11 engaging a groove 12 of gear 2 so that shaft 1% is coupled to the pump gear 2 for joint rotation but relative axial displacement.

The shaft is formed as a rotary valve member with an oblique groove 13 closed in itself and extending ali around the periphery of the shaft.

in the sense of rotation indicated by arrow 14 the gear pump sucks the fluid from the suction space 15 and forces it into the discharge space 16. The suction space 15 communicates through a bore 17 with the suction line 13. The discharge space 16 communicates through a bore 19 with the end 26 of the cylindrical bore 21 of the rotary valve member or shaft 10.

Thus the gear pump passes the fluid, e. g. the lubricant, from the pressure space 16 through the bore 19 into the space at the left-hand end of the rotary valve member 16. From there the fluid handled is passed under the handling pressure through a central bore 22 of the rotary valve member 19 and a transverse bore 23 into the oblique groove 13 and as the valve member revolves the fluid is distributed by the groove 13 alternately into the delivery passage 24 opening into the cylindrical bore 21, and into the axially spaced return passage 25 also opening into the cylindrical bore 21. That return passage 25 opens at 4% into the suction space 15 but the connecting passage is not shown in the drawing.

The delivery of the pump is adjusted by a set screw 27 cooperating with the right-hand end face 26 of the rotary valve member 16. The rotary valve member or shaft 16 is urged against said set screw by the handling pressure in space 29, in which a compression spring may be arranged additionally. The use of the handling pressure in the space 2 as the contact pressure, however. olfers the advantage that no sliding bearing face is required at the revolving rotary valve member 1%.

Depending on the axial adjustment of the rotary valve member il the fluid handled is passed through the oblique groove 13 and the delivery passage 24 to the outlet 25 for a longer or shorter time. in the position shown in the drawing the oblique groove does not wipe at all over the return passage 25 and the entire amount handled by the pump is passed into the outlet. if the rotary valve member i0 is displaced to the right because the set screw 27 has been screwed outwardly, the fluid handled will be passed into the return passage 25 for a certain period. in an intermediate position of the rotary valve member 10 the fluid handled is passed by the oblique groove 13 alternately to the delivery passage 2 and to the return passage 2-5. if the rotary valve member has been ad justed entirely to the right, the oblique groove 13 no longer wipes over the delivery passage at all during the entire rotation of the rotary valve member 18 the fluid handled is passed to the return passage 25 so that the pump has been set for zero delivery.

In the embodiment shown in Fig. 3 the fluid is again passed in an analogous manner from the discharge space, not shown in that figure, through a bore 29 to the oblique groove 30 of a rotary valve member 31, which latter is again formed by the shaft of the pump gear 2. Again the rotary valve member 31 is mounted in a cylindrical bore 32 of the casing 33 and the delivery passage 24 leading to the outlet 28 and the return passage 25 leading to the suction space not shown in that figure open at axially spaced points into that cylindrical bore 52. The connection of suction line 13 to the casing 33 is also omitted in the drawing.

The arrangement differs from the illustrative embodiment shown in Figs. 1 and 2 in that the space 34 at the right-hand end 35 of the rotary valve member Si is connicted through a bore 36 to the outlet 28 so that the delivery counter pressure in the space 3-: acts on the end face 35 of the rotary valve member. That delivery counter "ressure is opposed by the force of a spring 37, which through the intermediary of a thrust pin 38 exerts pressure on the left-hand end face 3% of the rotary valve member 31. The spring 37 balances the delivery counter pressure in the space 34 so that the rotary valve member 31 is axially displaced in dependence on the pressure at the outlet 28. An increased pressure at the outlet 28 will urge the rotary valve member 31 to the left against the action of spring 37 so that the oblique groove 30 is displaced towards the delivery passage 24 and the length of the period during which the fluid is passed into the outlet 2-3 is increased relative to the length of the period during which the fluid is returned through the passage 25. Thus an increase in the delivery counter pressure will cause an increase in the delivery of the pump and thus in the handling pressure in view of the delivery counter pressure. if the discharge line e. g. a lubricating line, connected to the outlet 28, is clogged, the increase in the delivery counter pressure will cause the delivery of the pump to be increased as much as to full capacity and the increase in the handling pressure will cause the resistance in the delivery line to be overcome or the clogging of the delivery line to be eliminated.

Reversely it may be necessary to reduce the delivery of the pump upon an increase of the delivery counter pressure. In that case an arrangement according to Fig. 4 is chosen, which differs from the arrangement shown in Fig. 3 only by the fact that the delivery passage and return passage are interchanged. The delivery passage 24' is displaced to the right, the return passage 25 to the left. Since the outlet 22 is again connected through a bore 36 to the space 34, the valve member is displaced to the left upon an increase in the delivery counter pressure, as in the arrangement shown in Fig. 3. Since the oblique groove 39 is thus moved towards the return passage 25', however, this causes a reduction in the delivery of the pump.

In the embodiment shown in Figs. 1 and 2 and in the embodiment shown in Figs. 3 and 4 the arrangement is suitably so that the lead of the oblique groove corresponds approximately to the axial distance between the opening of the delivery passage 24 or 24 and the opening of the return passage 25 or 25 or the like in the cylindrical bore so that the oblique groove 13 or 3i! can wipe over the outlet connection as well as the return passage in the intermediate position of the rotary valve member 19 or 31.

What I claim is:

1. In a device for controlling the delivery of a gear pump including a casing, a working chamber and two pump gears therein, said working chamber having a pump discharge space, a delivery passage and a return passage separated from the delivery passage in the casing, a cylindrical bore, the said cylindrical bore having a first recess in communication with said delivery passage and having a second recess in communication with said return passage spaced axially from the first recess, a rotary and axially movable valve member having a cylindrical surface within said cylindrical bore, the valve member operatively connected to and revolving in timed relation with said gears, and means in the said valve member for providing periodic communication of said first recess and said second recess with said discharge space.

2. In a device for controlling the delivery of a gear pump including a casing, a working chamber and two pump gears therein, said working chamber having a pump discharge space, a delivery passage and a return passage separated from the delivery passage, a cylindrical bore, a rotary and axially movable valve member having a cylindrical surface within said cylindrical bore, the valve member operatively connected to and revolving in timed relation with said gears, the cylindrical bore having a recess in communication with the said delivery passage and another recess in communication with the said return passage, the valve member having a recess in communication with the said discharge space and the last-mentioned recess interconnecting periodically the said discharge space with the said first-mentioned recess and the said second-mentioned recess.

3. In a device for controlling the delivery of a gear pump including a casing, a working chamber and two pump gears therein, said working chamber having a pump discharge space, a delivery passage and a return passage separated from the delivery passage, a cylindrical bore, a rotary and axially movable valve member having a cylindrical surface and an end surface within the cylindrical bore, the valve member operatively connected to and revolving in timed relation with said gears and having an oblique groove on the cylindrical surface thereof in communication with the said discharge space, the said cylindrical bore having a first recess in communication with said delivery passage and having a second recess in communication with said return passage spaced axially from the first recess, the said valve member having two end positions and intermediate positions between the end positions, the said oblique groove communicating the said discharge space periodically with the said delivery passage and the said return passage during the said intermediate positions of the valve member.

4. In a device according to claim 3, wherein means is provided for axially shifting the said valve member in order to vary the ratio of the durations of the discharge period and return period.

5. In a device according to claim 3, wherein the said oblique groove is closed in itself and extends all around the periphery of the cylindrical surface of the said valve member.

6. In a device according to claim 3, wherein an axle is axially slidable inserted in one of the said pump gears, the said valve member being constituted by the said axle.

7. In a device according to claim 3, wherein the lead of the said oblique groove corresponds approximately to the said axial distance between the said first and second recesses.

8. In a device according to claim 3, wherein an end space is provided in the said cylindrical bore closed up by the said end surface of the said valve member, the said end space being connected to a point of the way of the medium fed between the said discharge space and the said delivery passage.

9. In a device according to claim 3, wherein a set screw is provided for axially shifting the said valve member.

10. In a device according to claim 3, wherein an end space is provided in the said cylindrical bore closed up by the said end surface of the said valve member, the said end space being in communication with the said discharge space, and a set screw acting on the end of the said valve member opposite to the said end surface.

11. In a device according to claim 3, wherein an end space is provided in the said cylindrical bore closed up by the said end surface of the said valve member, the said end space being in communication with the said delivery passage and a pressure spring acting on the end of said valve member opposite to the said end surface.

12. In a device according to claim 11, wherein the second recess is arranged in communication with the said return passage at a point disposed nearer to the said end space than the said first recess which communicates with the said delivery passage.

13. In a device according to claim 11, wherein the said first recess is arranged in communication with the said delivery passage at a point disposed nearer to the said end space than the said second recess which communicates with the said return passage.

References Cited in the file of this patent UNITED STATES PATENTS 2,149,969 Lattner Mar. 7, 1939 2,159,720 Wahlmark May 23, 1939 2,309,195 Jirsa Jan. 26, 1943 2,333,885 Poulter Nov. 9, 1943 

